I say go. You'll likely have a great time.
One of our local shops has a similar ride and my guess is that your ride is geared to beginners. That said, ask the people at the shop how fast you're expected to be able to go and whether there's a "no drop" policy. Again, my guess is that don't leave anyone behind. Once you're there, don't be afraid to ask questions about group riding etiquette. Most cyclists are more than happy to help. Once the ride begins, just be cautious and observant and you'll do just fine.
Have fun!
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher